In a chain transmission device for driving a camshaft in which a timing chain is looped over a driving sprocket attached to a crankshaft and a driven sprocket attached to the camshaft, a pivotable chain guide is provided on one side of a slack side of the timing chain, and adjustment force of a chain tensioner is applied to a remote end of the chain guide remote from the center of pivoting motion of the chain guide to tighten the timing chain, thereby preventing the chain from slackening and flapping.
Another chain guide is fixed in position on the side of a tight side of the timing chain to guide the movement of the timing chain, thereby to prevent flapping of the chain.
As the chain guide for adjusting tensile force and for guiding the movement of the timing chain, a type of chain guide for guiding the surface of the timing chain by sliding contact is known. However, there is a problem that movement resistance of the timing chain is large and a transmission torque loss is significant.
In order to solve such a problem, the below-identified Patent Document 1 proposes a chain guide in which both ends of a plurality of roller shafts arranged in a curve form are supported by a guide base elongated in the moving direction of a timing chain, each of rollers formed by roller bearings is rotatably supported on each of the plurality of roller shafts, and the timing chain is movably supported by the plurality of rollers.
In the above chain guide, since the timing chain is guided by a roll of the plurality of rollers, there is a characteristic that the movement resistance of the timing chain is small and a transmission torque loss is insignificant.